you're a gun
Australian slang for "you're a champion", meaning you're the best or you otherwise very good at something.
A: "What's the square root of 256?"
B: "16"
A: "And what's that to the power of 3?"
B: "4096"
A: "Awesome. You're a gun!"
B: "16"
A: "And what's that to the power of 3?"
B: "4096"
A: "Awesome. You're a gun!"